US8528868B2 - Supporting device - Google Patents

Abstract

The present invention discloses a tripod, comprising a base; three legs pivotally provided around the base, each comprising a first tube and a second tube, which is telescopically assembled inside the first tube; first lock mechanisms disposed between the first tube and the second tube of each leg and locking the second tube relative to the first tube to prevent the telescopic movement of the second tube relative to the first tube; three groups of transmission chains, each extending from the base into each leg and coupled with the corresponding first lock mechanism to drive the corresponding first lock mechanism to lock or unlock the second tube; and an actuating mechanism, disposed in the base and synchronously coupled with the three groups of transmission chains to actuate them. The legs of a tripod provided by the present invention may be synchronously and quickly locked and thereby the tripod may be unfolded quickly.

Description

FIELD OF THE PRESENT INVENTION

The present invention relates to a supporting device for use in stabilizing and providing support to photographic equipment, or other instruments, devices or apparatus, and particularly to a tripod of which legs thereof can be quickly and synchronously locked.

BACKGROUND OF THE PRESENT INVENTION

In order to stabilize photographic equipment or other instruments for the purpose of shooting or operation, a tripod is usually used to support the photographic equipment or instrument. Such tripod typically comprises three telescopic legs and an object stage at the top of the legs for supporting the photographic equipment or instrument. During use, each of the three telescopic legs is extended, locked to a desired length, and unfolded to a desired inclination relative to the object stage and then the bottom thereof is settled on the ground. Lastly, a photographic equipment or an instrument is fixed on the object stage such that shooting or operation of the photographic equipment of the instructed can be conducted.

Conventional tripods in the market are advertised for their reduced weight, ease of portability, although it is rather complicated and time consuming to unfold for use or to fold for storage. Taking a three-section tripod with three tubes in each leg for example, the connection of the three tubes of each leg requires two joints, and the whole tripod requires six joints. In order to adjust each leg to a specific length, one needs to operate and juggle with at least two joints at the same time so that the upper and lower tubes can be connected together at relative locations. In other words, the installation of a tripod needs operation of six joints and this is rather complicated and time consuming.

For easy installation, the joints of most tripods adopt a “fast lock system”. Two adjacent tubes may be locked by flipping a latch of the fast lock system. Once a “clap” sound is heard the system is locked with the relevant adjacent tubes located against each other. Nevertheless, for a three-section tripod, the legs can be locked to the desired length only after six “claps”, so the tripods adopting a “fast lock system” are still unable to achieve the effect of fast installation. If the tripod is a four-section tripod comprising four tubes in each leg, the above installation and operation will be even more complicated and more time consuming.

In case a “snap shot” is needed when a sudden event arises and unfolding of a tripod is needed right away, the above defects will become even more apparent.

When shooting or operation is completed or shooting or operation needs to be continued in another place, the tripod needs to be folded. This reverse operation is equally complicated and time consuming.

Further, a glide tack is connected to the bottom of each leg, to settle the tripod on the ground. However, in order to adapt to different sites, a tripod kit typically includes plastic glide tacks and metal glide tacks for use in different circumstances. When the tripod is to be settled on hard ground (e.g. made of wood or marble) and the tripod needs to be protected, plastic glide tacks are connected to the bottom of the tripod to provide cushioning. When the tripod is to be settled on soft ground (e.g. snowy or softy ground) and the glide tacks need to be inserted into the ground, metal glide tacks are connected to the bottom of the tripod. In conventional tripods, when change of the glide tack is required the original glide tacks must be removed and replaced by another type of glide tacks. This makes the installation of the tripod even more complicated.

SUMMARY OF THE PRESENT INVENTION

To address the above problems, the present invention provides a tripod, comprising a base; three legs pivotally provided around the base, each comprising a first tube and a second tube telescopically assembled inside the first tube; first lock mechanisms, each disposed between the first tube and the second tube of each leg, and locking the second tube relative to the first tube to prevent the telescopic movement of the second tube relative to the first tube; three groups of transmission chains, each extending from the base into each leg and coupled with the corresponding first lock mechanism to drive the corresponding first lock mechanism to lock or unlock the second tube; an actuating mechanism, disposed in the base and synchronously coupled with the three groups of transmission chains to actuate them.

Further, the tripod may further comprise three groups of leg angle regulating units, each disposed between the base and each leg connecting piece in order to selectively lock the corresponding leg relative to the base and prevent the pivoting of the leg relative to the base; the three groups of leg angle regulating units are coupled with the actuating assembly so that the corresponding leg is unlocked relative to the base under the actuation of the actuating assembly.

The legs of the tripod provided by the present invention may be synchronously and quickly locked and thereby the tripod may be quickly unfolded.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other features and advantages will become more apparent from the following detailed description of the present invention by referring to the accompanying drawings in which the parts or the components are merely schematic and not drawn pro rata, in which:

FIG. 1 is a schematic of a folded tripod provided by the present invention;

FIG. 2 is a schematic of an unfolded tripod provided by the present invention;

FIG. 3 is a top view of the tripod shown inFIG. 1;

FIG. 4 is a cross-sectional view of a tripod provided by the present invention taken along a section A-A shown inFIG. 3;

FIG. 5 is a cross-sectional view of a tripod provided by the present invention taken along a section B-B shown inFIG. 3;

FIG. 6 is an exploded schematic of the base of a tripod provided by the present invention;

FIG. 7 is a cross-sectional view of the base of a tripod provided by the present invention taken along a section C-C shown inFIG. 4;

FIG. 8 is a bottom view of the turntable of a tripod provided by the present invention;

FIG. 9 is a top view of the turntable of a tripod provided by the present invention;

FIG. 10 is a schematic of the base of a tripod provided by the present invention taken along a section D-D shown inFIG. 4;

FIG. 11 is a schematic showing the state of the dust cover when the handle of a tripod prodded by the present invention is in a lifted state;

FIG. 12 is a schematic of the base of a tripod provided by the present invention taken along a section E-E shown inFIG. 4, and shows the state of the dust guard side plate when the handle of the tripod is in a locked state;

FIG. 13 is a schematic of the base of a tripod provided by the present invention taken along a section E-E shown inFIG. 4, and shows the state of the dust guard side plate when the handle of the tripod is in an unlocked state;

FIG. 14 is a side view of a folded tripod provided by the present invention with a partial cutaway;

FIG. 15 is a side view of an unfolded tripod provided by the present invention with a partial cutaway;

FIG. 16 andFIG. 17 are schematics showing the connecting relation between the base and the legs of a tripod provided by the present invention;

FIG. 18 is a cross-sectional view of a leg of a tripod provided by the present invention taker along a section F-F shown inFIG. 14;

FIG. 19 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section G-G shown inFIG. 14;

FIG. 20 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section H-H shown inFIG. 14;

FIG. 21 is a cross-sectional view of a leg of a tripod provided by the present invention take along a section I-I shown inFIG. 14;

FIG. 22 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section J-J shown inFIG. 14;

FIG. 23 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section K-K shown inFIG. 14;

FIG. 24 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section L-L shown inFIG. 14;

FIG. 25 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section M-M shown inFIG. 14;

FIG. 26 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section N-N shown inFIG. 15;

FIG. 27 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section O-O shown inFIG. 15;

FIG. 28 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section P-P shown inFIG. 15;

FIG. 29 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section Q-Q shown inFIG. 15;

FIG. 30 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section R-R shown inFIG. 15;

FIG. 31 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section S-S shown inFIG. 15;

FIG. 32 is a cross-sectional view of a leg of a tripod provided by the present invention along a section T-T shown inFIG. 15;

FIG. 33 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section U-U shown inFIG. 15;

FIG. 34 shows the positional relation between the turntable and each of the gears when the handle of a tripod provided by the present invention is in a locked state;

FIG. 35 shows the positional relation between the turntable and each of the gears when the handle of a tripod provided by the present invention is in an unlocked status;

FIG. 36 is a schematic showing the transmission relation of a tripod provided by the present invention;

FIG. 37 is a perspective view showing the initial state of the unlock unit of a leg of and provided by the present invention;

FIG. 38 is a schematic showing the initial state of the unlock unit of a leg of a tripod provided by the present invention;

FIG. 39 is a perspective view showing the working state of the unlock unit of a leg of a tripod provided by the present invention;

FIG. 40 is a schematic showing the working state of the unlock unit of a leg of a tripod provided by the present invention;

FIG. 41 is a cross-sectional view showing the connecting relation between a glide tack and a leg of a tripod provided by the present invention;

FIG. 42 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section V-V shown inFIG. 41;

FIG. 43 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section W-W shown inFIG. 41;

FIG. 44 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section X-X shown inFIG. 41;

FIG. 45 is a cross-sectional view of a leg of a tripod provided by the present invention talon along a section Y-Y shown inFIG. 41;

FIG. 46 is a schematic showing the suction stroke of the damping device of a tripod provided by the present invention;

FIG. 47 is a schematic showing the exhaust stroke of the damping device of a tripod provided by the present invention;

FIG. 48 is a cross-sectional view of a leg of a tripod provided by the present invention taken along a section Z-Z shown inFIG. 41, and shows the glide tack assembly locating unit of a tripod provided by the present invention;

FIG. 48A is a schematic of the curved groove of the glide tack assembly locating unit in a tripod provided by the present invention;

FIG. 49 is a schematic showing the glide tack assembly of a tripod provided by the present invention is in an extended state; and

FIG. 50 is a schematic showing the glide tack assembly of a tripod provided by the present invention is in a retracted state, wherein the glide tacks have been replaced by metal glide tacks.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

As shown inFIG. 1 andFIG. 2, the tripod of the present invention mainly comprises: abase1; three legs2 pivotally provided on the base, acenter shaft3 vertically passing through the base and vertically movable relative to the base, and acenter shaft lock4 assembled on the center shaft and locking the center shaft relative to the base. Each leg2 of the tripod provided by the present invention at least has two tubas and may have three or more tubes. In the examples shown in the drawings, each leg2 has fourtubes5,6,7 and8. Preferably, as shown inFIG. 3, three legs2 are evenly distributed on the circumference of thebase1.

As shown inFIGS. 3-14, thebase1 comprises a main body11, aninner cover14 snap-fit to the main body11 and anouter cover15 disposed on theinner cover14. Aturntable12 and anactuating assembly13 engaged with theturntable12 and actuating it are rotatably disposed between the main body11 and theinner cover14. Further, three groups offirst gears17 are disposed spaced with each other on the lateral part of the main body11 and between the main body11 and theinner cover14 in order to contact theturntable12. Three groups ofsecond gears18 andthird gears19 engaged with each other are also disposed spaced with each other on the lateral part of the main body11.

The main body11 of the base comprises: abottom basin110 with a concave111 accommodating theturntable12 formed on its upper surface; astand column112 extending upward from the center of thebottom basin110 and forming a center hole to deceive thecenter shaft3 and forming an external thread113 on the external surface of its upper part; anannular locating slot114 formed around thestand column112 and in the concave111, and with a pair of opposite stop bumps1141 formed therein (seeFIG. 7); three groups ofbrackets115 spaced with each other and extending outwards from the sidewall of the bottom basin110 (seeFIG. 6 andFIG. 14), each group of the brackets comprising two spaced cantilevers used to support thesecond gear18 and thethird gear19; afirst opening116 near each of thebrackets115 and formed on the sidewall of the bottom basin, through which theoutput shaft20 connecting thefirst gear17 extends out of the main body11; asecond opening117 inside each of the brackets and formed on the side of thebottom basin110, through w thesecond gear18 contacts with theturntable12 inside the concave111; and afirst shield118 formed below each of thefirst opening116. In order to easily discharge the water or impurities in thebottom basin110, a plurality ofdiversion holes1142 passing through thebottom basin110 may be formed inside the locatingslot114.

Theturntable12 as a whole is in a shape of a truncated cone and is formed with aenter hole120, for easy assembly onto thestand column112 of the main body of the base. Theturntable12 comprises a pair of locatingblocks121 facing with each other and formed on the bottom surface of the turntable. Thereby when theturntable12 is installed in the main body11, the locating blocks121 will be settled in thelooting slot114 of the main body of the base. Aspring122 is disposed between eachlooting block121 and thecorresponding stop bump1141 in the locatingslot114 of the main body of the base, and tends to push thelocating block121 against another stop bump (seeFIG. 7). An annular concave123 is formed on the outside of the lower surface of theturntable12. Threeracks124 spaced with each other are formed on the co gave123 (seeFIG. 8) to selectively engage with thesecond gears18 respectively. On the conical side of theturntable12, a plurality ofteeth125 are formed around the circumference of the turntable (seeFIG. 9) to engage with thefirst gear17. A counter bore126 is formed on the upper surface of theturntable12 and around thecenter hole120, to receive theactuating assembly13. Asemicircle guide slot127 is formed inside the counter bore126 and around thecenter hole120. In order to easily discharge the water or impurities in theturntable12, a plurality ofdiversion holes1271 that pass through theturntable12 may be formed inside theguide slot127.

The actuatingassembly13 comprises: abottom plate130 contained in the counter bore126 of the turntable; acenter hole131 formed at the center of thebottom plate130, for being assembled on thestand column112 of the main body of the base; and aguide block132 extending downward from the bottom surface of thebottom plate130, and seated in theguide slot127 of the turntable when the actuatingassembly13 is installed into theturntable12. A pair ofsprings133 is disposed in theguide slot127 of the turntable. The two ends of each spring are against one end of the semicircle guide slot127 and theguide block132, respectively, for tending to make theactuating assembly13 stay in a central balanced position (seeFIG. 10). The actuatingassembly13 further comprises asupport134 extending upward from the top surf ice of thebottom plate130 and ahandle135 pivotally engaging on the top end of thesupport134, wherein the height of thesupport134 is determined such that its top end is above theinner cover14 of the base and the end of thehandle135 extends out of theouter cover15 of the base.

Theinner cover14 of the base is formed with acenter hole140, for being assembled on thestand column112 of the main body of the base and on thesupport134 of the actuating assembly. A counter bore141 corresponding to the counter bore126 of the turntable is formed on the bottom surface of theinner cover14 of the base, and nap fit to thebottom plate130 of the actuating assembly to cooperate with the counter bore126 of the turntable to limit the longitudinal displacement of the actuatingassembly13. Three spaced concave receivingslots142 are disposed on the bottom surface of theinner cover14 of the base, to receive thefirst gears17 respectively and make thefirst gears17 engaging with theteeth125 on the side of the turn able. Asecond shield143 is formed on the side of the inner cover of the base at the location opposite thefirst shield118 of the main body of the base. The first shield and the second shield form a semi-cylinder upper shield (seeFIG. 5). After theinner cover14 is snap fitted to the main body11 of the base, the two may be fastened through connecting pieces, such as bolts (seeFIG. 4), to limit the longitudinal displacement of the assemblies contained therebetween.

Theouter cover15 of the base forms anaccommodation cavity150 in which thesupport134 of the actuatingassembly13 and the inner end of thehandle135 rotate. Moreover, acenter hole151 is formed at the center of its top to assemble it on thestand column112 of the main body of the base. Anopening152 is formed on the sidewall of theouter cover15 of the base, through which the external end of thehandle135 extends out of the outer cover. A “T” shapedprotrusion153 is formed in the opening152 (seeFIG. 1). Thereby, thehandle135 may rotate from one side of the “T” 3shaped protrusion to the other side thereof and realize the switchover between a locked state and an unlock state. The switchover will be described in details below.

Thebase1 may also comprise afastening nut16 that screws on theexternal thread1131 on the upper part of thestand column112, to press theouter cover15 against theinner cover14, wherein theexternal thread1131 is formed below the external thread113 and its outer diameter is greater than that of the external thread113.

Thecenter shaft3 is assembled in the center hole of thestand column112 of the base and its upper end is provided with anobject stage31. At the center of the top surface of theobject stage31, ascrew rod32 is provided to connect photographic equipment or instrument (not shown in the figures). At the bottom end of thecenter shaft3, acounter weight hook33 may be provided to hang counter weights (not shown in the figures) so as to stabilize the tripod.

Thecenter shaft lock4 comprises amain body41 and anannular wedge42. Acenter hole410 is formed in themain body41 of the lock.Internal thread411 is formed on the inner wall of the center hole. The diameter of the upper end of thecenter hole410 is smaller than the diameter of its lower end. Theinternal thread411 of the main body of the lock engages with the external thread113 at the top end of thestand column112. Meanwhile, theannular wedge42 is disposed between thestand column112 and thecenter shaft3 inside thecenter hole410. When the position of thecenter shaft3 needs to be locked, the main body of the lock will be tightened more tightly to the external thread113, thereby squeezing theannular wedge42 downward, making it more tightly wedge into the space between the stand column and the center shaft and achieving the aim of locking the center shaft. When thecenter shaft3 needs to be loosened, theannular wedge42 will be relaxed by loosening themain body41 of the lock.

Further, in order to reduce the dust entering the base, which may block the movable components in the base, anupper dust cover21 may be disposed inside theaccommodation cavity150 of theouter cover15 of the base. Theupper dust cover21 comprises anopening211 that allows thestand column112 to pass through and apivot212 around which theupper dust cover21 pivots (seeFIG. 12). Upper andlows strutting pieces213 and214 that are snap-fit to each other are disposed on the outer cover and the inner cover of the base, respectively, to strut thepivot212. Asupport chip215 extends from thepivot212 in a direction away from theupper dust cover211. Aspring216 is disposed between the support chip and thelower strutting piece214, and thespring216 tends to push thesupport chip215 upward, so as to preps theupper dust cover21 against the handle135 (seeFIG. 4). Therefore, when thehandle135 moves along the “T” shapedprotrusion153, theupper dust cover21 will cling to thehandle135 and move with it together (seeFIG. 11).

Further, in order to prevent dust from entering thebase1 from theopening152, a pair of arc dustguard side plates22 may be disposed around the inner wall of theouter cover15 of the base. The dustguard side plates22 are respectively disposed on the two sides of thehandle135 and may be slidably settled in theannular groove144 on the top surface of theinner cover14 of the base. Each dustguard side plate22 is towed by aspring221, the two ends of eachspring221 are respectively fixed to a side of the corresponding dustguard side plate22 that farther from thehandle135 and theouter cover15 of the base, for tending to press the dustguard side plate22 against the handle135 (seeFIG. 12 andFIG. 13). Therefore, when thehandle135 moves along the “T” shaped protrusion inside theopening152, the dustguard side plate22 will cling to thehandle135 and move with it together.

FIGS. 14-40 show the connecting relation between the legs2 and thebase1 of a tripod provided by the present invention. The legs in the present invention are same in structure, so here only one leg is described.

The leg2 is connected to thebase1 through theleg connecting piece23. Theleg connecting piece23 is fixed to the top end of thefirst tube5 of the leg and includes a pair of connectingsheets231 extending straight up from its upper surface. This pair of connectingsheets231 spans the two sides of thebracket115 of the base and is pivotally connected to thebracket115 by aid of thesupport shaft232 of thethird gear19. A legangle regulating lever24 is disposed between thethird gear19 and the top surface of theleg connecting piece23, theend241 of the regulating lever near the inner side of the leg is pivotally connected to theleg connecting piece23, while the end thereof near the outer side of the leg is a free end. A plurality ofteeth243 are formed in the middle of the upper surface of the regulatinglever24 facing thethird gear19, to engage with thethird gear19; while the middle part of its lower surface facing theleg connecting piece23 is supported by aspring242 tending to push the teeth in the middle of thelever24 against the third gear19 (seeFIG. 5).

A connectingprotrusion233 is formed on theleg connecting piece23 at the location close to the connectingsheet231, and on it, a semi-cylinderlower shield25 assembled into the upper shield is disposed.

Theoutput shaft20 of eachfirst gear17 extends into the protective cavity formed by respective upper and lower shields, and its tail end is connected to afirst pawl26. Asecond pawl27 engages with thefirst pawl26. Thesecond pawl27 is also in a protective cavity and itsoutput shaft28 extends into the leg2 and is pivotally connected to the firstcolumnar transmission shaft281 inside the leg2. Thefirst pawl26 and thesecond pawl27 may be six-prong pawls. When the leg2 rotates relative to thebase1, the connectingsheet231 of theleg connecting piece23 will rotate relative to thebracket115 of the base, and meanwhile thelower shield25 will rotate inside the upper shield, until the lower shield and/or the connecting protrusion come against the lower edge of the upper shield. In this process, thefirst pawl26 and the second pa it27 always engage with each other (seeFIGS. 16 and 17).

As shown inFIG. 14 andFIG. 15, each leg2 in the present invention comprises four tubes, i.e.first tube5,second tube6,third tube7 and fourth tube8. Thefirst tube5 comprises atubular shell51. The upper and lower ends of theshell51 are open, and its upper end is connected to theleg connecting piece23. Two groups of locatingholes52 are formed on the inner wall of theshell51 along the full height of theshell51. The two groups of locatingholes52 are distributed in angular symmetry relative to the center of theshell51, and comprise a plurality of vertically aligned locating holes521 (seeFIG. 18 andFIG. 26). Astop block53 is formed at the bottom of the inner wall of theshell51, to prevent thesecond tube6 from being completely moved out of thefirst tube5, which will be described in details below.

Thesecond tube6 comprises atubular shell61 assembled in theshell51 of the first tube in a vertically movable manner. A mountingbracket62 is fixed to the upper end of theshell61 and comprises spaced upper and lower supporting plates. The firstcolumnar transmission shaft281 passes through the mountingbracket62, and may rotate freely relative to the mountingbracket62. A stressedgear63 and awork gear64 are held between the upper and lower supporting plates of the mountingbracket62 in a vertically overlapped manner, and assembled on the firstcolumnar transmission shaft281. The cross section of the center hole of the stressedgear63 is rectangular and it is determined that its size is slightly greater than the size of the cross section of the firstcolumnar transmission shaft281, thereby when the stressedgear63 is assembled on the first columnar transmission shaft, it may slide along the lengthwise direction of the first columnar transmission shaft, but may not rotate relative to the firs columnar transmission shaft (seeFIG. 19 andFIG. 28). However, it is determined that the size of the center hole of thework gear64 should enable its free rotation relative to the first columnar transmission shaft when it is assembled on the first columnar transmission shaft (seeFIG. 20 andFIG. 28). The stressedgear63 and thework gear64 are connected via aspring65. One end of the spring is fixed to the stressedgear63 and the other end thereof is fixed to thework gear64. Thereby, when the firstcolumnar transmission shaft281 rotates and drives the stressedgear63 to rotate, the stressedgear63 will drive thework gear64 to rotate together by aid of thespring65.

Apin2811 and awasher2812 are disposed at the lower end of the firstcolumnar transmission shaft281. Thewasher2812 is disposed on the mountingbracket62. The inner hole of thewasher2812 is rectangular and its size is slightly greeter than the size of the cross section of thecolumnar transmission shaft281. Thereby, thewasher2812 may prevent thepin2811 from entering the center hole of thework gear64.

The drivengear66 is held between the upper and lower supporting plates of the mountingbracket62, and engages with the stressedgear63. The secondcolumnar transmission shaft282 is connected to the drivengear66 in a fixed manner and extends downward freely rotatable relative to the mountingbracket62. For example, the drivengear66 is formed with a center hole with a rectangular cross section (seeFIG. 19), and it is determined that its size is slightly greater than the size of the secondcolumnar transmission shaft282, thereby when the drivengear66 is assembled on the second columnar transmission shaft, it can not rotate relative to the second columnar transmission shaft.

Further, apin2821 and awasher2822 are disposed on the second columnar transmission shaft adjacent to the upper and lower supporting plates of the mountingbracket62. Thewasher2822 is between thepin2821 and the upper/lower plates, thereby preventing the longitudinal movement of the secondcolumnar transmission shaft282 relative to the driven gear66 (seeFIG. 29). Meanwhile, as thewasher2822 may disperse the longitudinal thrust of the secondcolumnar transmission shaft282 to the mountingbracket62, it may ensure the two ends of the drivengear66 won't endure excessive longitudinal thrust.

Thesecond tube6 of the leg further comprises astop unit69 and athrust spring692 disposed inside the mounting bracket62 (seeFIG. 21 andFIG. 30). One end of thestop unit69 is pivotally disposed inside the mountingbracket62 and comprises astop protrusion691 extending outward towards the mountingbracket62. One end of thethrust spring692 is against the mountingbracket62 and the other end is against the stop unit, for tending to push thestop protrusion691 out of theopening611 that run through theshell61 and the sidewall of the mountingbracket62. Therefore, when the upper end of thesecond tube6 slides to the tail end of thefirst tube5, thestop protrusion691 of thestop unit69 will contact and press against thestop block53 of the first tube from the top, thereby preventing thesecond tube6 from sliding out of thefirst tube5.

In order to lock the second tube relative to the first tube when the second tube of the leg is retracted, thesecond tube6 further comprises alock unit67 disposed on one side of the work gear64 (seeFIG. 20 andFIG. 37). The lock unit comprises: abase plate671; arack672 at the end of the base plate facing thework gear64, which engages with the work gear; and acrotch673 at the end of thebase plate671 opposite the end that forms the rack. Thecrotch673 comprises at least onelocating pin6731 that cooperates with the locatinghole521 on thefirst tube5. Meanwhile, anopening612 that allows thelocating pin6731 to pass through is formed on the shell and the mountingbracket62 of thesecond tube6 Thereby, when thework gear64 rotates clockwise (view from top), it will drive thebase plate671 by aid of therack672 to move towards the opening612, so that thelocating pin6731 ofcrotch673 passes through the mounting bracket and shell and enters the locatinghole521 of thefirst tube5, thereby locking the first tube and second tube and disabling the stretching of the second tube.

Preferably, to maintain balance, anotherlock unit68 may be provided for thesecond tube6. Thelock unit68 and thelock unit67 are arranged in angular symmetry relative to thework gear64, thereby the locating pin of the crotch may be selectively inserted into a locating hole of another group of locating holes in the first tube. As the two lock units have a roughly same structure, detailed description for thelock unit68 is net provided here for clarity purpose.

In order to finely adjust the length of the section of thefirst tube5 extending out of thesecond tube6 when the whole leg position is locked, aunlock unit60 may be disposed on thesecond tube6. The unlock unit comprises: atraction unit601 disposed at the lower part of theshell61 of the second tube; anactuating block602 disposed on the side surface of the lockunit base plate671; anactuating wedge603 near theactuating block602 and disposed inside the mountingbracket62 in a vertically movable manner; athrust spring604, with the two ends thereof being against the mountingbracket62 and theactuating wedge603 respectively, for tending to plush theactuating wedge603 away from theactuating block602; and atraction rope605, with one end thereof fixed to theactuating wedge603 and the other end thereof passing through theshell61 of thesecond tube6 and fixed to the traction unit601 (seeFIG. 27). Thetraction unit601 comprises aframe6011 fixed to the external surface of the shell; aswivel arm6012 pivotally disposed on theframe6011; and apress tablet6013 connected to the free end of theswivel arm6012. Thepress tablet6013 is preferably inside theconcave groove6014 formed on one side offrame6011. Thetraction rope605 is fixed to one end of thetraction unit601, i.e. fixed to the press tablet6013 (seeFIG. 38).

Thereby, when thepress tablet6013 is pressed, thetraction rope605 will drive the actuatingwedge603 to overcome the thrust of thethrust spring604 and move downward, thus push thelock unit67 to move towards the inside of the mountingbracket62 by aid of theactuating block602, thereby thelocating pin6731 is moved out of the locatinghole521, and thesecond tube6 is unlocked and can move relative to totefirst tube5.

In the case that thesecond tube6 comprises alock unit68, therack672 of thelock unit67 drives thework gear64 to rotate anticlockwise (view from top), and drives thelock unit68 to move towards the inside of the mountingbracket62 in the same time, thereby the locating pin of thelock unit68 is also moved out from the locating hole of the first tube to unlock the locking between the first tube and the second tube (seeFIG. 39 andFIG. 40).

After the position of thesecond tube6 relative to thefirst tube5 is adjusted and thepress tablet6013 is released, thethrust spring604 will push the actuating wedge away from theactuating block602, thereby under the restoring force of the spring thework gear64 will re-rotate clockwise and drive the two lock units to move towards the outside of the mountingbracket62, thus re-locking thesecond tube6 relative to thefirst tube5.

Further, two groups of locatingholes613 are formed on theshell61 of the second tube in the location stagger with the group of locatingholes52 of thefirst tube5 and along the full height of theshell61. Each of the two groups of locatingholes613 comprises a plurality of vertically aligned locating holes6131 (seeFIG. 36). Additionally, astop hole614 is formed at the bottom of theshell61 of the second tube6 (seeFIG. 15), to prevent thethird tube7 from being completely moved out of thesecond tube6, which will be described in details below.

A longitudinal throughhole721 is formed on the mountingbracket72 of thethird tube7 in the location corresponding to the firstcolumnar transmission shaft281, and allows the firstcolumnar transmission shaft281 to pass through when the leg is retracted (seeFIG. 21 andFIG. 22). When the upper end of thethird tube7 slides to the tail end of thesecond tube6, thestop protrusion791 of thestop unit79 of thethin tube7 will be engaged with thestop hole614 of thesecond tube6, thereby preventing thethird tube7 from sliding out of thesecond tube6. Additionally, thelock units77 and78 of thethird tube7 adopt a stagger layout with respect to thelock units67 and68 of the second tube6 (seeFIG. 36). Thereby, the clockwise rotation of thework gear74 of the third tube7 (view from top) may drive thelock units77 and78 to move towards inside of the mountingbracket72. Except the foregoing difference, thethird tube7 and thesecond tube6 are structurally similar, and detailed description for thethird tube7 is not provided here clarity purpose.

As shown inFIG. 15 andFIGS. 32-33, a first longitudinal throughhole821 is formed on the mountingbracket82 of the fourth tube8 in the location corresponding to the firstcolumnar transmission shaft281, and allows the firstcolumnar transmission shaft281 to pass through when the leg is retracted; and a second longitudinal throughhole822 is formed at the location corresponding to the secondcolumnar transmission shaft282, and allows the secondcolumnar transmission shaft28 to pass through when the leg is retracted (seeFIGS. 24-25 andFIG. 32). Thelock units87 and88 of the fourth tube8 adopt a stagger layout with respect to thelock units77 and78 of the third tube7 (seeFIG. 36). Thereby, the anticlockwise rotation of thework gear84 of the fourth tube8 (view from top) may drive thelock units87 and88 to move towards inside of the mountingbracket82. Additionally, if the fourth tube8 is the last tube of the leg, the tube may not include the driven gear and the columnar transmission shaft disposed in a fixed manner relative to the driven gear. Except the foregoing difference, the fourth tube8 and thethird tube7 are structurally similar, and detailed description for the fourth tube8 is not provided here for clarity reason.

The operation of the tripod in accordance with the present invention will be described in further detail with reference toFIGS. 34-36.

When thehandle135 of the actuatingassembly13 is in the locking position as shown inFIG. 34, i.e. on the right of the “T” shaped protrusion as shown inFIG. 1, the guide block132 of the actuatingassembly13 will be in a balanced position in theguide slot127 of theturntable12 and make theturntable12 stay in its initial position under the action of thespring122. In this case, thesecond gear18 and theracks124 of the turntable engage with each other, so thesecond gear18 is unable to rotate freely. As thesecond gear18 engages with the third gear19 (seeFIG. 5), and thethird gear19 meshes with theteeth243 of the legangle regulating lever24, thethird gear19 is unable to rotate, and the legangle regulating lever24 is unable to rotate relative to thethird gear19. Therefore, the legangle regulating lever24 with one end disposed on the leg in a fixed manner may block the leg from rotating relative to thebase1 and from opening outward.

At the same time, as theturntable12 maintains still, thefirst gear17 that engages with theteeth125 on its side also maintains still, thereby itsoutput shaft20 andpawl26 won't drive the firstcolumnar transmission shaft281 of the leg to rotate. Therefore, the lock units of the second to fourth tubes of the leg are in the initial position in which they extending out of the corresponding shells, while their respective locating pins are also in the initial state in which they are inserted into the locating holes of the upper tubes. Therefore, all neighboring tubes of each leg are in the locked state and can't stretch.

When thehandle135 of the actuatingassembly13 rotates to the unlocked position as shown inFIG. 35, i.e. on the left of the “T” shaped protrusion as shown inFIG. 1, the guide block132 of the actuatingassembly13 will rotate clockwise in theguide slot127 of the turntable12 (view from top), and under the push of the spring133G, theturntable12 will rotate clockwise together. Owing to the rotation of theturntable12, thesecond gear18 is disengaged with therack124 of the turntable. Therefore, by now, thesecond gear18 may freely rotate in the annular concave123 of theturntable12. As thesecond gear18 engage-a with the third gear19 (accFIG. 5), while thethird gear19 engages with theteeth243 of the legangle regulating lever24, thus thethird gear19 may rotate too, thereby the legangle regulating lever24 may drive thesecond gear18 and thethird gear19 to rotate. Therefore, when the leg is rotated relative to thebase1, the legangle regulating lever24 with one end disposed on tie leg in a fixed manner may drive thesecond gear18 and thethird gear19 to freely rotate without any blockage. Thus each leg2 may rotate relative to thebase1 to unfold a certain angle.

In the same time, as theturntable12 rotates clockwise, thefirst gear17 that engages withteeth125 on its side will rotate anticlockwise (view outwards from inside of the base), thereby theoutput shaft20 of the first gear will drive the firstcolumnar transmission shaft281 of the leg to rotate anticlockwise (view from top) via thefirst pawl26, thesecond pawl27 and theoutput shaft28 of the second pawl. The firstcolumnar transmission shaft281 drives the stressedgear63 to rotate anti clockwise, while the stressedgear63 will drive thework gear64 via thespring65 to rotate anticlockwise, thereby thework gear64 drives thelock units67 and68 to move towards the inside of the mountingbracket62 by the aid of the racks, so that the lock pins of the lock units move out of the locating holes in thefirst tube5, and thefirst tube5 and thesecond tube6 of the leg are unlocked.

In the same time, the stressedgear63 drives the drivengear66 to rotate clockwise (view from top), and the drivengear66 drives the secondcolumnar transmission shaft282 to rotate clockwise together. Similar to the above operation, the secondcolumnar transmission shaft282 drives the stressedgear73 of thethird tube7 to rotate clockwise, and the stressedgear73 drives thework gear74 via thespring75 to rotate clockwise, thereby thework gear74 drives lockunits77 and78 by the aid of the racks of thelock units77 and78 to move towards the inside of the mountingracket72 so that the lock pins of the lock units of the third tube move out of the locating holes of thesecond tube6 and thesecond tube6 and thethird tube7 of the leg are unlocked.

Thethird tube7 and the fourth tube8 are unlocked in the same way. Therefore, by the above transmission mode, the locking of all neighboring tubes of each leg is unlocked and each tube is pulled out to a specific length from the respective upper tube.

After the length of each leg and its angle relative to the base are adjusted, thehandle135 may be turned to the locked position, i.e. the position on the right of the “T” shaped protrusion as shown inFIG. 1, to lock the legs. When thehandle135 is turned to the locked position, theturntable12 will be turned to the position shown inFIG. 34 under the action of thespring122, thereby thesecond gear18, thethird gear19 and the legangle regulating lever24 of each leg is relocked. As a result, the angle between each leg and the base will be locked.

Further, in the process when theturntable12 is turned to the position shown inFIG. 34, it drives thefirst gear17 of each leg to rotate clockwise (view outwards from inside of the base), thereby the columnar transmission shaft, the stressed gear, the work gear and the driven gear in each tube will rotate in a direction reverse to the direction of the unlock operation and drive the lock units of each tube to move towards the outside of respective mounting brackets. As a result, the lock pin of each lock unit will re-enter a locating hole of the group of locating holes of the upper tube, to relock the neighboring tubes of each leg.

Thereby, after the stretched length and unfolded angle of each leg are adjusted, the present invention may synchronously lock all the legs by simply turning thehandle135 back to the locked position, i.e. the position on the right of the “T” shaped protrusion as shown inFIG. 1, including the unfolded angle of each leg relative to the base and the stretched length of each leg.

When the handle is in the locked position, in order to finely adjust the unfolded angle each leg relative to the base, the free end of the legangle regulating lever24 may be pressed (seeFIG. 5), to overcome the elastic force of thespring242 and disengage theteeth243 of the regulating lever from thethird gear19, thereby the leg2 may freely rotate relative to thebase1 and free from the restriction of the inability of thesecond gear18 andthird gear19 in rotation.

Likewise, when the handle is in the locked position, in order to finely adjust the stretched length of each tube, the press tablet of its unlock unit may be pressed (seeFIGS. 37-40), to make the traction rope drive the actuating wedge to move downward against the thrust of the thrust spring, thereby pushing the lock unit by the aid of the actuating block to move towards the inside of the mounting bracket. As a result, the locating pin moves out of the locating hole and the locking between this tube and its upper tube may be released.

The glide tack assembly at the end of each leg in a tripod provided by the present invention will be described below by referring toFIGS. 41-50.

Theglide tack assembly9 is disposed in the last tube of each leg, for example, the fourth tube8 in this example, and comprises asupport frame91 disposed inside the fourth tube of the leg in a vertically movable manner, a glidetack selection unit92 disposed at the lower end of the support frame, afirst glide tack93 fixed to the glide tack selection unit, asecond glide tack94 fixed to the glide tack selection unit and opposite to the first glide tack, atension spring95 with one end thereof fixed to thesupport frame91 and the other end thereof fixed to the fourth tube, anair damping unit96 disposed between the fourth tube and the support frame, and a glide tackassembly locating unit97.

The top end of thesupport frame91 is open and formed with acavity911 that allows the insertion of the columnar transmission shaft of the corresponding tube. Further,channels912 and913 are formed in thecavity911 and allow the insertion of the firstcolumnar transmission shaft281 and the secondcolumnar transmission shaft282, respectively. The size of each channel is slightly greater than the size of the cross section of the corresponding columnar transmission shaft, so that the columnar transmission shaft may freely rotate in the channel and get in and out from the channel. Meanwhile, the size of each channel is only slightly greater than the size of the cross section of the columnar transmission shaft, when the tripod is folded and horizontally stored, the corresponding columnar transmission shafts will be in the channels and supported by the sidewalls of the channels. This may avoid the bending of transmission shafts otherwise resulting from long-time suspension of their tails.

Thefirst glide tack93 andsecond glide tack94 may be made from different materials, to adapt to the requirements of different sites. For example, thefirst glide tack93 may be made from plastic to apply to indoor sites; and thesecond glide tack94 may be made from metal to apply to outdoor sites.

As shown inFIG. 49, the glidetack selection unit92 comprises: aplummer921, which is rotatably disposed at the lower end of thesupport frame91, while thefirst glide tack93 and thesecond glide tack94 are disposed on the opposite sides of theplummer921 respectively; aselector dial922, which is disposed at the central position of theplummer921 relative to thesupport frame91 in a fixed manner and symmetrically forms twogrooves9221 and9222 on its circumference; and aselection spring leaf923, which is in a U shape and hasprotrusions9231 and9232 facing inside of the U shape at its two ends. The distance between the protrusions of theselection spring leaf923 is slightly smaller than the diameter of theselector dial922, the middle location of theselection spring leaf923 is fixed to theplummer921, and the twoprotrusions9231 and9232 are against theselector dial922 along the diameter of theselector dial922. Thereby, when theplummer921 is rotated to select glide tacks, the two protrusions of theselection spring leaf923 will slide along the circumference of theselector dial922 till into the groove of theselector dial922, to realize locating of the glide tack. The glide tack can be switched over simply by rotating theplummer921 by 180° to make the two protrusions of theselection spring leaf923 slide into the groove of the respective selector dial.

When to glide tack needs to be switched over, the lower end of thesupport frame91 should be pulled out of the fourth tube8 of the leg. After that, theplummer921 of the glide tack selection unit may be rotated to select a glide tack. After the glide tack has been switched over, the pulling force of thetension spring95 may pull thesupport frame91 and the glidetack selection unit92 carried on it back into the fourth tube8, and only the selected glide tack is exposed.

In order to prevent thetension spring95 from suddenly pulling thesupport frame91 back into the fourth tube8 to injure the user, anair damping unit96 may be installed between thesupport frame91 and the fourth tube8. As shown inFIG. 46 andFIG. 47, the air damping unit comprises: a firstvertical cylinder961; asecond cylinder962 transversely fixed to the end of the first cylinder and communicated with the first cylinder; apiston963 movably disposed inside the first cylinder, and apiston rod964 connected to thepiston963. Anair inlet9621 is formed in the sidewall of the second cylinder; adiaphragm9622 is disposed on the inner wall of the cylinder at a location corresponding to theair inlet9621, to cover this air inlet. Thediaphragm9622 is fixed on the edge farthest from the first cylinder, while other edges are free. Further, anair outlet9623 is further formed on the wall of the second cylinder. The size of theair outlet9623 is much smaller than that of theair inlet9621. Therefore, where thepiston963 is drawn by thepiston rod964 away from the second cylinder, air will enter the first cylinder and second cylinder mainly via theair inlet9621, thereby thepiston963 may slide quickly. When thepiston963 approaches the second cylinder under the push of thepiston rod964, the air in the first cylinder and second cylinder needs to be discharged. However, the air that needs to be discharged presses thediaphragm9622 against theair inlet9621. As a result, the air is unable to be discharged from theair inlet9621 and can be discharged only from the very smallsized air outlet9623. In this way, when thepiston963 approaches the second cylinder, it will meet with large air resistance and can move slowly only.

The first cylinder and the second cylinder of the air damping unit are inside the fourth tube and fixed to the fourth tube or the support frame of the glide tack assembly, while their piston rods are relatively fixed to the support frame or the fourth tube. Therefore, due to the foregoing operation mode of the air damping unit, when thesupport frame91 is pulled out of the fourth tube8, the pistons may move quickly, thereby thesupport frame91 may be pulled out quickly. However, when thetension spring95 pulls thesupport frame91 back into the fourth tube8, the piston can move slowly only due to air damping. Consequently, thesupport frame91 can only move slowly into the fourth tube8, thereby playing a safe and protective role.

Further, when the glidetack selection unit92 is pulled out of the fourth tube8 to perform switchover of glide tacks, in order to overcome the pulling force of thetendon spring95 and prevent thesupport frame91 and glidetack selection unit92 from being automatically pulled back into the fourth tube8, a glide tackassembly locating unit97 may be disposed inside the fourth tube8. The glide tackassembly locating unit97 comprises a locatingrod971, acurved groove972 formed on the support frame, and aspring973 for pressing an end of the locatingrod971 against thecurved groove972. One end of the locatingrod971 is disposed on the fourth tube8, and the other end is engaged in thecurved groove972 in a slidable manner. Thecurved groove972 is a heart-shaped curved groove (seeFIG. 48A). It comprises thecurse segments9721,9722,9723 and9724, which are connected by turn. The depth of the intersections of the segments is greater than the depth of the curve segments, and the depth of the starting point of the latter curve segment is slightly greater than the depth of the end point of the former curve segment, thereby it may be ensured that the end of the locatingrod971 won't enter a wrong curve segment or slide backwards. Further, thecurve segment9721 may be formed with afree end9720 not intersected with other curve segments. When thesupport frame91 and the glidetack selection unit92 are inside the fourth tube8, the slidable end of the locatingrod971 will be at thefree end9720 of thecurve segment9721. When thesupport frame91 is pulled out of the fourth tube8, the slidable end of the locating rod will slide upward along thecure segment9721. When thesupport frame91 is fully pulled out, the slidable end will slide to the first intersection betweencurve segments9721 and9722. When thesupport frame91 is released, due to the traction of thetension spring95, thesupport frame91 will partly retract to the fourth tube8 of the leg, thereby the slidable end of the locatingrod971 will slide along thecurve segment9722 to the second intersection between thecurve segment9722 and thecurve segment9723, and be in a stable state here to prevent thesupport frame91 from further retracting to the fourth tube8. When the selection of glide tacks is completed and thesupport frame91 and the glidetack selection unit92 retract into the fourth tube8, thesupport frame91 needs to be pulled outward at first, to make the slidable end of the locatingrod971 leave the second intersection, arrive at the third intersection between thecurve segment9723 and thecurve segment9724 along thecurve segment9723, pass the third intersection and enter into thecurve segment9724. At this moment, if thesupport frame91 is released, thewhole support frame91 and glidetack selection unit92 swill retract to the fourth tube8 under the traction of thetension spring95. Meanwhile, the slidable end of the locatingrod971 will slide along thecurve segment9724, enter thecurve segment9721, and slide to thefree end9720 of thecurve segment9721 in the end, thereby thesupport frame91 and the glide tack selection units:92 stably retract to the fourth tube8.

Further, abottom cover98 may be disposed at the end if the fourth tube8, to cover the area of the end of the fourth tube8 not covered by theglide tack assembly9.

Achannel981 may be disposed in thebottom cover98. Its structure and function are the same as those of thechannels912 and913, to accommodate and carry other columnar transmission shafts and avoid the bending of transmission shafts otherwise resulting from long-time suspension of their tails. At the bottom of thebottom cover98,diversion hole982 running through thebottom cover98 may be formed, so that the rater and impurities are discharged from each leg.

Though the embodiments of the present invention have been illustrated above, those skilled in the art may further change and modify the present invention. It should be understood that such changes and modifications are within the spirit and range of the present invention.

Claims (32)

The invention claimed is:

1. A tripod comprising:

a base;

three legs pivotally provided around the base, each comprising a first tube and a second tube telescopically assembled inside the first tube;

first lock mechanisms, each disposed between the first tube and the second tube of each leg, and locking the second tube relative to the first tube to prevent the telescopic movement of the second tube relative to the first tube;

three groups of transmission chains, each extending from the base into each leg and coupled with the corresponding first lock mechanism to drive the corresponding first lock mechanism to lock or unlock the second tube;

an actuating mechanism, disposed in the base and synchronously coupled with the three groups of transmission chains to actuate them;

wherein the base comprises a main body and an outer cover snap-fit to the main body; the main body of the base comprises a bottom basin with a concave formed on the upper surface, a stand column extending upward from the center of the bottom basin, and three groups of brackets spaced with each other and extending outwards from the sidewall of the bottom basin; the outer cover of the base is formed with a center hole for being assembled on the stand column;

wherein, the tripod further comprises three groups of leg connecting pieces, each leg connecting piece is fixed to the top end of the first tube of the leg and includes a connecting sheet extending straight up from its upper surface, the connecting sheet is pivotally connected to the corresponding bracket on the base;

wherein the actuating mechanism comprises:

a turntable formed with a center hole for being assembled on the stand column and received into the concave of the bottom basin rotatable around the stand column, and formed with a plurality of teeth on the side face of the turntable and around its circumference; and

an actuating assembly comprising:

a bottom plate formed with a center hole for being assembled on the stand column and engaged with the turntable in such a manner that the bottom plate may actuate the turntable;

a support extending upward from the upper surface of the bottom plate; and

a handle which is pivotally engaged on the top end of the support and the external end of which extends out of the outer cover of the base;

wherein an opening that allows the external end of the handle to extend out is formed in the sidewall of the outer cover of the base, a “T” shaped protrusion is formed in the opening, and the handle may move from one side of the “T” shaped protrusion to the other side thereof;

wherein the first tube comprises a tubular shell with open upper and lower ends; the second tube comprises a tubular shell with open upper and lower ends and with a cross section shape the same as that of the shell of the first tube, and a mounting bracket engaged on the top end of the shell of the second tube and including spaced upper and lower supporting plates;

wherein the first lock mechanism comprises:

a group of first locating holes formed on the inner wall of the shell of the first tube along the lengthwise direction of the first tube, which comprises a plurality of vertically aligned locating holes; and

a first lock unit disposed in the mounting bracket of the second tube orthogonally to the group of first locating holes, wherein the first lock unit comprises a first base plate, and at least one first locating pin is formed at the end of the first base plate close to the group of first locating holes; an opening is formed on the shell of the second tube at the location corresponding to the first locating pin to allow the first locating pin entering into or retracting from the first locating hole when it extending out of or retracting into the mounting bracket of the second tube;

wherein each transmission chain comprises:

a first gear disposed to engage with the teeth on the side of the turntable;

a first columnar transmission shaft which is coupled with the output shaft of the first gear, passes the corresponding leg connecting piece, extends into the corresponding leg, and freely rotatably runs through the mounting bracket of the second tube; and

a first stressed gear and a first work gear sandwiched between the upper and lower supporting plates of the mounting bracket of the second tube in a vertically overlapped manner, wherein a first traction spring is disposed between the first stressed gear and the first work gear, one end of the first traction spring is fixed to the first stressed gear and the other end thereof is fixed to the first work gear;

wherein, the first stressed gear is assembled on the first columnar transmission shaft in such a manner that it may move longitudinally but can't rotate relative to the first columnar transmission shaft, while the first work gear is assembled on the first columnar transmission shaft in such a manner that it may move longitudinally and rotate relative to the first columnar transmission shaft; and

wherein, a first rack that engages with the first work gear is formed in a section of the first base plate of the first lock unit facing the first work gear.

2. The tripod according toclaim 1, wherein the first stressed gear is formed with a center hole with a rectangular cross section and the size of which is determined slightly larger than the size of the cross section of the first columnar transmission shaft.

3. The tripod according toclaim 1, wherein the bottom basin further comprises an annular locating slot formed around the stand column and in the concave, and a pair of opposing stop bumps are formed inside the locating slot; the turntable comprises a pair of opposing locating blocks formed on the bottom surface of the turntable and located inside the locating slot; wherein a spring is disposed between one of the stop bumps and one of the locating blocks for tending to push the locating block against the other stop bump.

4. The tripod according toclaim 3, wherein a counter bore is formed on the upper surface of the turntable to receive the bottom plate of the actuating assembly; the turntable further comprises a semicircle guide slot formed around its center hole and inside the counter bore; the actuating assembly further comprises a guide block that extends downward from the bottom surface of the bottom plate, the guide block is located inside the guide slot, a pair of springs are disposed inside the guide slot, the two ends of each spring are against one end of the guide slot and the guide block, respectively, for tending to make the bottom plate of the actuating assembly stay in the central balanced position.

5. The tripod according toclaim 1, wherein the base further comprises an inner cover held between the main body and the outer cover of the base and snap-fit on the bottom plate of the actuating assembly: a center hole is formed in the inner cover for being assembled on the stand column and the support; an annular receiving slot is formed on the circumference of the bottom of the inner cover to receive the first gear.

6. The tripod according toclaim 5, wherein the tripod further comprises an upper dust cover disposed between the outer cover and the inner cover of the base and pressing from the above against the handle, and the upper dust cover comprises an opening that allows the stand column to pass through and a pivot around which the upper dust cover pivots; and upper and lower strutting pieces that are snap-fit to each other are disposed on the outer cover and inner cover of the base respectively, to strut the pivot;

wherein, the upper dust cover further comprises a support chip that extends from the pivot in a direction reverse to the opening direction of the upper dust cover, a spring is disposed between the support chip and the lower strutting piece, and the spring tends to push the support chip upward so as to press the upper dust cover against the handle.

7. The tripod according toclaim 5, wherein the tripod further comprises a pair of arc dust guard side plates disposed around the inner wall of the outer cover of the base, the dust guard side plates are disposed on the two sides of the handle respectively and slidably seated in the annular groove on the top surface of the inner cover of the base;

wherein, each dust guard side plate is towed by a spring, the two ends of each spring are fixed to the lateral part of the corresponding dust guard side plate farther from the handle and the outer cover of the base respectively, for tending to press the dust guard side plate against the handle from the two sides of the handle.

8. The tripod according toclaim 5, wherein the output shaft of each first gear extends out of the base, and engages with the first columnar transmission shaft through a pair of pawls.

9. The tripod according toclaim 8, wherein the pair of pawls are six-prong pawls.

10. The tripod according toclaim 8, wherein a semi-cylinder upper shield is formed on the lateral part of the base at the location corresponding to the output shaft of the first gear, a semi-cylinder lower shield is disposed on each leg connecting piece and assembled inside the upper shield, and the pair of pawls are contained in the protective cavity formed by the upper and lower shields.

11. The tripod according toclaim 1, wherein the shell of the first tube further comprises a stop block formed at the bottom of its inner wall; the second tube further comprises a first stop unit and a first thrust spring disposed in the mounting bracket of the second tube; one end of the first stop unit is pivotally provided in the mounting bracket of the second tube and includes a first stop protrusion that extends towards the outside of the mounting bracket of the second tube and aligns with the stop block; one end of the first thrust spring is against the mounting bracket of the second tube and the other end thereof is against the first stop unit for tending to push the first stop protrusion out of the opening formed in the shell of the second tube and corresponding to the first stop protrusion.

12. The tripod according toclaim 1, wherein each leg of the tripod further comprises a first unlock unit used to unlock the second tube relative to the first tube, and the first unlock unit comprises a first traction unit disposed in the lower part of the shell of the second tube; a first actuating block disposed on the first base plate of the first lock unit and between the first rack and the first locating pin; a first actuating wedge near the first actuating block and vertically movably disposed inside the mounting bracket of the second tube; a first thrust spring, the two ends of which are against the mounting bracket of the second tube and the first actuating wedge, respectively, for tending to push the first actuating wedge away from the first actuating block; and a first traction rope, one end of which is fixed to the first actuating wedge and the other end of which passes through the shell of the second tube and is fixed to the first traction unit.

13. The tripod according toclaim 12, wherein the first traction unit comprises: a first frame fixed to the outer surface of the shell of the second tube; a first swivel arm pivotally provided on the first frame; and a first press tablet engaged with the free end of the first swivel arm, wherein the first traction rope is fixed to the first press tablet at the first traction unit.

14. The tripod according toclaim 1, wherein the tripod further comprises:

a center shaft, which vertically passes through the base and is vertically movable relative to the base; and

a center shaft lock assembled on the center shaft to lock the center shaft relative to the base.

15. The tripod according toclaim 14, wherein a center hole is formed in the stand column; and the center shaft is assembled in the center hole of the stand column, and an object stage for carrying photographic equipment or other instruments is disposed on the upper end of the center shaft.

16. The tripod according toclaim 15, wherein a screw rod is disposed at the center of the top surface of the object stage to connect the photographic equipment or other instruments, and a counter weight hook for hanging counter weights is disposed at the bottom end of the center shaft.

17. The tripod according toclaim 15, wherein the center shaft lock comprises a main body and an annular wedge, the main body of the center shaft lock has a center hole with internal thread formed in the inner wall thereof, and the diameter of the upper end of the center hole is smaller than the diameter of the lower end thereof; external thread is formed on the external surface of the upper part of the stand column to engage with the internal thread; and the annular wedge is disposed inside the center hole of the main body of the center shaft lock and between the stand column and the center shaft.

18. The tripod according toclaim 1, wherein each leg further comprises at least a third tube, the at least third tubes are assembled together in a mutually telescopic manner and assembled as a whole into the second tube in a mutually telescopic manner; and each of the at least third tubes comprises a tubular shell with open upper and lower ends and with a cross section shape the same as that of the shell of the second tube, and a mounting bracket engaged with the top end of the shell of the at least third tubes and including spaced upper and lower supporting plates.

19. The tripod according toclaim 16, wherein a second lock mechanism is disposed between the second tube and the neighboring third tube, which locks the internal tubes of the neighbor tubes relative to the external tube thereof so as to prevent the telescopic movement of the internal tubes relative to the external tube; and the second lock mechanism comprises:

a group of second locating holes formed on the inner wall of the shell of the external tube of the neighboring tubes along the lengthwise direction of the leg, which comprises a plurality of vertically aligned second locating holes, wherein two directly neighboring groups of locating holes among the group of first locating holes and the group of second locating holes are disposed in a mutually staggered manner; and

a second lock unit disposed in the mounting bracket of the internal tube of the neighboring tubes orthogonally to the group of second locating holes, wherein the second lock unit comprises a second base plate, and at least one second locating pin is formed at the end of the second base plate that is close to the group of second locating holes; wherein an opening is formed on the shell of the external tube of the neighboring tubes at the location corresponding to the second locating pin so as to allow the second locating pin entering into or retracting from the second locating hole when it extending out of or retracting into the mounting bracket where it is located.

20. The tripod according toclaim 17, wherein each transmission chain further comprises:

at least a group of second stressed gears and second work gears, wherein each group of second stressed gears and second work gears are sandwiched between the upper and lower supporting plates of the mounting bracket of the internal tube of the neighboring tubes in a vertically overlapped manner, a second traction spring is disposed between the second stressed gears and second work gears, one end of the second traction spring is fixed to the second stressed gear and the other end is fixed to the second work gear;

at least a driven gear, each held between the upper and lower supporting plates of the mounting bracket of the external tube of the neighboring tubes, and engaging with the corresponding first stressed gear or second stressed gear;

at least a second columnar transmission shaft, each connecting the driven gear in the external tube of the neighboring tubes and the second stressed gear and second work gear inside the internal tube of the neighboring tubes;

wherein, the driven gear is assembled on the corresponding second columnar transmission shaft in such a manner that it can't move longitudinally or rotate relative to the second columnar transmission shaft; the second stressed gear is assembled on the corresponding second columnar transmission shaft in such a manner that it can move longitudinally and can't rotate relative to the second columnar transmission shaft; and the work gear is assembled on the corresponding first columnar transmission shaft in such a manner that it can move longitudinally and rotate relative to the second columnar transmission shaft;

wherein, a second rack that engages with the corresponding second work gear is formed on the part of the second base plate of the second lock unit that faces the corresponding second work gear; and

wherein, a through hole that aligns with the first columnar transmission shaft and the at least second columnar transmission shaft is formed in the mounting bracket of the internal tube of the neighboring tubes, to allow the insertion of the first columnar transmission shaft and the at least second columnar transmission shaft.

21. The tripod according toclaim 20, wherein the shell of the external tube of the neighboring tubes further comprises a stop hole formed at the bottom of its side wall; the internal tube of the neighboring tubes further comprises a second stop unit and a second thrust spring disposed in its mounting bracket; one end of the second stop unit is pivotally provided in the mounting bracket of the internal tube of the neighboring tubes and includes a second stop protrusion that extends towards the outside of the mounting bracket of the internal tube of the neighboring tubes and aligns with the stop hole; one end of the second thrust spring is against the mounting bracket of the internal tube of the neighboring tubes and the other end thereof is against the second stop unit, for tending to push the second stop protrusion out of the opening formed in the shell of the internal tube of the neighboring tubes corresponding to the second stop protrusion.

22. The tripod according toclaim 20, wherein each leg of the tripod further comprises a second unlock unit used to unlock the internal tube of the neighboring tubes relative to the external tube of the neighboring tubes, and the second unlock unit comprises a second traction unit disposed in the lower part of the shell of the internal tube of the neighboring tubes; a second actuating block disposed on the second base plate of the second lock unit and between the second rack and the second locating pin; a second actuating wedge near the second actuating block and vertically movably disposed inside the mounting bracket of the internal tube of the neighboring tubes; a second thrust spring, the two ends of which are against the mounting bracket of the internal tube of the neighboring tubes and the second actuating wedge respectively, for tending to push the second actuating wedge away from the second actuating block; and a second traction rope, one end of which is fixed to the second actuating wedge and the other end of which passes through the shell of the internal tube of the neighboring tubes and is fixed to the second traction unit.

23. The tripod according toclaim 22, wherein the second traction unit comprises: a second frame fixed to the outer surface of the shell of the internal tube of the neighboring tubes; a second swivel arm pivotally provided on the second frame; and a second press tablet engaged with the free end of the second swivel arm, wherein the second traction rope is fixed to the second press tablet at the second traction unit.

24. The tripod according toclaim 1, wherein the tripod further comprises three groups of legs angle regulating units, each disposed between the base and each leg connecting piece in order to selectively lock the corresponding leg relative to the base and prevent the pivoting of the leg relative to the base; the three groups of legs angle regulating units are coupled with the actuating assembly so that the corresponding leg is unlocked relative to the base under the actuation of the actuating assembly.

25. The tripod according toclaim 24, wherein each group of brackets comprises two spaced cantilevers; an opening is formed on the sidewall of the bottom basin within the range limited by each bracket; an annular concave is formed on the outside of the lower surface of the turntable, and three sections of spaced racks are formed on the concave at the location corresponding to the opening on the sidewall of the bottom basin; and each leg angle regulating unit comprises:

a second gear; which is rotatably provided between the cantilevers of the corresponding bracket and engages with the corresponding rack of the turntable via the opening on the sidewall of the corresponding bottom basin;

a third gear, which is rotatably provided between the cantilevers of the bracket outside the second gear and engages with the second gear; and

a leg angle regulating lever, one end of which facing the inner side of the leg is pivotally connected to the corresponding leg connecting piece and the end near the outer side of the leg is a free end; a portion of which facing the third gear is formed with a plurality of teeth to engage with the third gear; and a portion of which facing the corresponding leg connecting piece is supported by a spring for tending to push the teeth of the leg angle regulating lever against the third gear.

26. The tripod according toclaim 25, wherein the tripod further comprises the glide tack assemblies provided at the ends of the legs, each comprising: a support frame; a glide tack selection unit provided at the lower end of the support frame; a first glide tack and a second glide tack opposite with each other fixed to the glide tack selection unit; a tension spring with one end thereof fixed to the support frame and the other end thereof fixed to the leg; and an air damping unit and a glide tack assembly locating unit provided between the support frame and the leg.

27. The tripod according toclaim 26, wherein the first glide tack and the second glide tack are made from different materials respectively.

28. The tripod according toclaim 27, wherein the glide tack selection unit comprises:

a plummer, which is rotatably provided under the support frame and carries the first glide tack and the second glide tack on its two opposite lateral parts;

a selector dial, which is fixed at the central position of the plummer relative to the support frame and symmetrically forms two grooves along the diameter on its circumference; and

a selection spring leaf, which is in a U shape and has protrusions facing the inside of the U shape at its two ends, wherein the distance between the protrusions of the selection spring leaf is slightly smaller than the diameter of the selector dial, the middle portion of the selection spring leaf is fixed to the plummer, and the two protrusions are against the circumference of the selector dial.

29. The tripod according toclaim 28, wherein the air damping unit comprises:

a first cylinder disposed along the lengthwise direction of each leg;

a second cylinder transversely fixed to the end of the first cylinder and communicated with the first cylinder , wherein an air inlet and an air outlet are formed on the sidewall of the second cylinder, and the size of the air outlet is much smaller than the size of the air inlet;

a piston slidably provided inside the first cylinder;

a piston rod connected to the piston; and

a diaphragm, which covers the air inlet on the inner wall of the second cylinder, with the edge farthest from the first cylinder being fixed and other edges being free;

wherein the first cylinder is fixed to one of the leg and the support frame, and the piston rod is connected to the other of the leg and the support frame.

30. The tripod according toclaim 29, wherein the glide tack assembly locating unit comprises a locating rod, a curved groove formed on the support frame, and a spring used to press one end of the locating rod against the curved groove; wherein one end of the locating rod is provided on the support frame and the other end thereof is slidably engaged in the curved groove; the curved groove is a heart shaped curved groove consisting of a plurality of curve segments, the depth of the intersections of neighboring curve segments is slightly greater than the depth of the curve segments, and the depth of the starting point of the latter curve segment is slightly greater than the depth of the end point of the former curve segment.

31. The tripod according toclaim 25, wherein the top end of the support frame is open and is formed with a cavity that allows the insertion of the first columnar transmission shaft and/or the second columnar transmission shaft, a plurality of first channels are formed inside the cavity and allow the insertion of the first columnar transmission shafts and/or second columnar transmission shafts, wherein the size of each first channel is determined slightly greater than the size of the cross section of the first columnar transmission shafts and/or the second columnar transmission shafts in such a way that the first columnar transmission shafts and/or second columnar transmission shafts can freely rotate in the corresponding first channels and get in and out from the corresponding first channels, and when the tripod is folded and horizontally stored, the first columnar transmission shafts and/or the second columnar transmission shafts are inserted into the corresponding first channels and supported by the sidewall of the first channels.

32. The tripod according toclaim 31, wherein a bottom cover is provided in the area not covered by the glide tack assembly at the end of each bracket, a plurality of second channels are provided in the bottom cover, the second channels allow the insertion of other first columnar transmission shafts and/or second columnar transmission shafts except those inserted into first channels, the size of each second channel is determined slightly greater than the size of the cross section of the other columnar transmission shafts in such a way that the other columnar transmission shafts can freely rotate in the corresponding second channel and get in and out from the corresponding second channel, and when the tripod is folded and horizontally stored, the other columnar transmission shafts are inserted into the corresponding second channels and supported by the sidewall of the second channels.

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